Radio direction finder system



4Dec. 24, 1946. H. c, BAUMANN 2,412,959

RADIO DIRECTIONFINDER SYSTEM Filed May l, 1943 HMH SEA/SE ANTENNA El rra/mfr Patented Dec. 24,1946

RADIO DIRECTION FINDER SYSTEM Harold C. Baumann, Elizabeth,

Federal rlelephorle & Radio York, N. Y., a corporation of N. J., assignor to Corporation, New Delaware Application May 1, 1943, Serial No. 485,273

6 Claims.

This invention relates to radio direction finders and especially to direction nding systems which utilize both a directional antenna and a sense antenna. In systems of this type the impulses received on the sense antenna are combined with impulses from the directional antenna to show the directional sense of the line of direction which may be derived from the latter impulses alone; that is, to show which end of said line points toward the transmitter. For this purpose the sense antenna impulses must be `shifted in phase until they are in phase opposition with one of the maxima of the directional antenna impulses and in phase with the other maximum.

For this purpose the receiving channel connected to the sense antenna is coupled to the directional antenna receiving channel through a phase shifting network, and the combined impulses are passed through suitable amplifying and detecting circuits to operate a direction indicator. It has been found that when the various wavelengths of different transmitting stations to which the antennae may be tuned vary substantially in frequency, the operation and effect of the phase shifting network are affected, and compensation of some type is desirable. Moreover, the network introduces a loss in the radio frequency circuits that tends to reduce eiiiciency.

A purpose of the invention is to provide a receiving and amplifying system for direction finders of the indicated type in which the phase shifting network is unaffected by changes in in coming signal frequency. Other objects are to eliminate losses due to said network in the radio frequency circuits which may affect efficiency, and to provide a better signal to noise ratio.

These purposes are in general accomplished by employing a superheterodyne amplifier with separate mixer or frequency converter tubes in each of the separate antenna circuits, and connecting the phase shifting network between the mixer tube output to modulate the directional antenna output impulses with impulses from the sense antenna in proper phase to produce a resultant impulse which will indicate the sense of the line of direction on the indicator. The modulated output is passed through a suitable intermediate frequency amplier followed by any suitable type of detecting and amplifying system adapted to operate a, direction indicator such as a cathode ray tube.

This arrangement has several advantages. operating the phase shift network only at the xed intermediate frequency regardless of changes in the frequency of the signals in the the use of band switching antenna circuits, uniform high eiiiciency and accuracy'are obtained. This permits the design and adjustment of the antenna systems to receive a wide band of frequencies, and specifically arrangements, without affecting the eiiiciency or operation of the phase shifting network. Moreover, the losses which are inevitable in the use of such a network are in-1 serted in the intermediate frequency portion of the 'circuits,.where they arenot as important, instead of in the radio frequency circuits, Where they may seriously affect eiiciency.

Other objects and advantages will appear from the following description considered in, connection with the accompanying drawing which illus-- trates one embodiment of the invention in diasrammatic form.

In this embodiment the sense antenna I0 is coupled through a radio frequency amplifier I I toan intermediate frequency mixer or converter .I2-coupled to oscillator I3 in the usual manner. Directional antennaY Ie is coupled through radio frequency amplifier I5 to the intermediate frequency mixer or converter I6, which likewise is coupled to oscillator I3. The output frequencies of mixer I2 and I6 will therefore be the same, each modulated by the amplified impulses received from the respective antennas.

The output of mixer I6 is modulated by the output of mixer I2 through a phase shift network Il arranged to adjust the phase of impulses from mixer I2 to synchronism with those from mixer I6 in a well known manner. The network disclosed includes capacitor I8 and variable resistor I9 in series in line 20 connecting the output circuits of said mixers. The output circuit of mixer I6 is coupled through transformer 2I to intermediate frequency amplifier 22 whose output is converted in known manner into a form suitable for operating a direction indicator, as by an audio frequency detector and amplifier system 23 coupled to direction finder 24 which may be a cathode ray tube.

While a preferred embodiment has been described, this has been done by way of illustration and not limitation since other arrangements and constructions may be employed without departing from the scope of the invention as set forth in the claims.

What is claimed is: 1

1. A radio direction finder receiving circuit arranged for directional antenna means, arranged for coupling to a means, frequency converting system including a coupling to a nona receiving circuit directional antenna means for converting the signal Waves in each receiving circuit t the same intermediate frequency, output circuits for said frequency converting means, phase shifting means in one of said output circuits, means for combining the intermediate frequency Waves from said output circuits in a common circuit, and a single detector and indicator circuit coupled to said common circuit.

2. A radio direction finder system including a receiving circuit arranged for coupling to a sense antenna, a receiving circuit arranged for coupling to a directional antenna, means for ccnverting signal Waves in each circuit to a common intermediate frequency, means operative on said intermediate frequency for shifting the phase of the intermediate frequency waves from the sense antenna circuit into phase synchronisrn with the intermediate frequency waves from the directional antenna circuit, means for combining thc- Waves from both circuits in a common circuL, and a single detector and indicator circuit coupled to said common circuit.

3. A radio direction finder system including a receiving circuit arranged for coupling to av sense antenna, a receiving circuit arranged for coupling to a directional antenna, means for separately converting signal Waves in each circuit to the same intermediate frequency including a mixer tube in each circuit, an intermediate frequency oscillation generator associated with both mixer tubes, a phase shifting network connected between the output circuits of the'mixer tubes, an intermediate frequency amplifier coupled to the output circuit of one of said tubes and a single detector and indicator circuit coupled to the Vintermediate frequency amplifier circuit.

4. A radio direction finder system including a receiving circuit arranged for coupling to a nondirectional antenna means, a receiving circuit arranged for coupling to a directional antenna means, frequency converting means for converting the signal Waves in each receiving circuit to the same intermediate frequency, phase shifting means directly connected with the output of one of the frequency converting means, means for combining the intermediate frequency WavesI from the outputs of said frequency converting means in a common circuit, a single intermediate frequency amplifier coupled With the combining means, and a single detector and indicator circuit coupled to said intermediate frequency amplifier.

5. A radio direction finder system including a receiving circuit arranged for coupling to a sense antenna, a receiving circuit arranged for coupling to a directional antenna, means for converting signal waves in each circuit to a common intermediate frequency, means directly connected with the converting means and operative on said intermediate frequency for shifting the phase of the intermediate frequency Waves from the sense antenna Acircuit into phase synchronism with the intermediate frequency Waves from the directional antennav circuit, means f or combining the waves from both circuits in a common circuit, a single intermediate frequency amplifier coupled with the combining means, and a single. de;- tector and indicator circuit coupled to said intermediate frequency amplifier.

6. A radio direction finder system inciuding a receiving circuit arranged for coupling toa sense antenna, a receiving circuit arranged for coupling to a directional antenna, means for separately converting signal Waves in each circuit to the same intermediate frequency including a mixer tube in each circuit, an intermediate frequency oscillation generator associated with both mixer tubes, a phase shifting network connected between the output circuits of the mixer tubes and combining the Wavesv from both circuits, a single intermediate frequency amplifier circuit coupled to the output circuit of one of said tubes, and a single detector and indicator circuit: coupled to the intermediate frequency amplifier circuit.

HAROLD C.k BAUMANN. 

